Pump with pressure loaded bushing



J. A. COMPTON 2,823,61 7

PUMP WITH PRESSURE LOADED BUSHING Feb. 18, 1958 Original Filed Dec. 14, 1949 iinited States 2,823,617 Patented Feb. 18, 1958 PUMP WITH PRESSURE LOADED BUSHING James A. Compton, South Euclid, Ohio, assignor to Borggarner Corporation, Chicago, 111., a corporation of linois Continuation of application Serial No. 132,934, Decemher 14, 1949. This application November 2, 1955, Serial No. 544,458

16 Claims. (Cl. 103-126) This application is a continuation of my copending application Serial No. 132,934, filed December 14, 1949, now abandoned.

As is well known, in a pressure loaded pump a part of the discharge pressure is applied to the rear or motive surfaces of the axially movable pressure loadable bushing, or bushings where a plurality of pumping elements are employed as in a gear pump, to urge the bushing into sealing engagement with the associated pumping element. As disclosed in U. S. Patent No. 2,420,622 to Roth et al., by carefully selecting the relative areas of the forward surfaces of the bushings and of the motive surfaces of the bushings in an intermeshing gear type pump, it is possible to control within very close limits the actual sealing pressure provided. In practice, this requires a somewhat higher effective pressure in the direction of seal than in the direction tending to open the seal.

In the type of pressure loaded pump described in the above patent, the motive or loading chamber to which discharge pressure is supplied will be uniformly subjected to the discharge pressure. That is to say, at all points on the motive surfaces at the rear of the bushing, substantialiy the same pressure will exist. Therefore, where, as in a conventional intermeshing gear type pressure loaded pump, the motive surface comprises an annulus concentrically disposed with respect to the axis of the pumping gear, the loading force is uniform about the axis of the pump. On the other hand, the forward surfaces of the bushing, that is, the surface adjacent the pumping element side surface, while uniformly disposed with respect to the axis of the bushing, is not subjected to a uniform fluid pressure. Since the pressure across the forward surfaces of the bushing extends from the minimum value corresponding to inlet pressure in the area adjacent the inlet of the pump to a maximum value corresponding to discharge pressure adjacent the discharge of the pump, the pressure across the gear side face engaging surface gradually increases from inlet to discharge pressure. Accordingly, it will be evident that while the total pressure forces acting on the motive or loading surfaces of the bushing may be made to equal or to exceed the total pres sure forces acting on the forward surfaces of the bushing, the pressures acting on all opposite points of the two bushing surfaces will not be so proportioned and the portion of the forward bushing surface nearer the inlet being subjected to a lesser pressure tending to break the seal than the portion of the forward bushing surface nearer the outlet of the pump, an unbalanced pressure condition results, tending to twist the bushing in the pump housing and producing uneven wear. Wear is, of course, concentrated on the inlet side of the pump.

As set forth in the co-pending application of Frederick C. Haberland, S. N. 130,904, filed December 3, 1949, the unbalanced condition resulting from the pressure gradient acting across the forward surfaces of the bushing may be compensated by offsetting the pressure responsive motive surface of the bushing so that a lesser area of the motive surface is exposed on the inlet side of the pump than on the discharge side. This is accomplished by employing a bushing having a flanged end adapted to engage the pumping element side surface and offsetting the periphery of the barrel portion in the direction of the inlet side of the pump. The resultant, generally annular, motive surface area has a markedly less width adjacent the inlet side of the pump than adjacent the outlet side. '1" ierefore, since the force exerted is a function of the pressure and the area, a proportionately greater force is exerted on the discharge side of the motive surface than on the inlet side, thus compensating for the pressure gradient across the forward surface of the bushmg.

The arrangement described in the above-mentioned Haber-land application requires a special pump housing, that is, the bushing receiving cavity must also be offset to accommodate the offset barrel portion. It has been found in practice that it is somewhat difficult to achieve in production the considerable degree of eccentricity required without unduly increasing the cost of manufacture. Furthermore, as will be readily apparent, the Haberland arrangement is not suitable for modifying pumps already in use, that is to say, because of the housing modification required, it is not practical to incorporate this improvement in pressure loaded pumps already constructed.

An object of the present invention is to provide a new and improved pressure loaded pump, and more particularly, a pressure loadable bushing assembly adapted for incorporation in a conventional pump housing Without modification of the housing and which bushing assembly will provide a graduated pressure responsive motive surface.

In accordance with one embodiment of this invention,

a pressure loaded type intermeshing gear pump having one set of auxiliary movable, pressure loadable bushings may be provided wherein the axially movable bushings each comprise an axially apertured, two-piece bushing assembly. The bushing assembly includes a cover element, the forward surface of which is adapted to engage the side surface of the pumping element of the pump in sealing relation and the exposed rear surface of which provides the motive or pressure loadable surface of the bushing assembly. The rear surface of the cover element is provided with a deep, cylindrical recess, the axis of which is offset with respect to the axial aperture extending through the cover element in the direction of the inlet side of the pump. The barrel portion of the bushing, comprising the second element of the assembly, is provided with a plurality of axiaily spaced, radially extending flanges and has an offset, cylindrical, raised portion or boss on its forward surface adapted to be received in the recess formed in the cover and to be sealed thereto by a sealing ring disposed in a groove formed about the periphery of the raised portion. The axial thickness of the assembly from the forward surface of the cover to the rearmost flanged surface is selected to be equivalent to the normal thickness of the flange provided on a conventional pressure loadable bushing. The assembly is, therefore, interchangeabie with the conventional bushing with out modification of the housing.

Other objects and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the drawings wherein:

Fig. 1 is a fragmentary, axial, sectional view of a pressure loadable intermeshing gear type pump having a pair of bushing assemblies in accordance with this invention;

Fig. 2 is a transverse, sectional view taken substantially along the line 22 of Fig. 1; and

Fig.3 is a sectional view taken substantially along the line 33 of Fig. 2.

Referring now to the drawings, and particularly to Fig. 1 thereof, a pump similar to that shown in the aforementioned Roth et al. patent, except for the bushing arrangement, is there illustrated having a sectional housing comprising a main body portion 5 and a left closure member 6. These sections are securely bolted together and cooperate to define a pair of parallel axes, intersecting bores or pumping gear chambers 7 and 8 which are arranged to receive in complementary relationship intermeshing pumping gears 9 and 1t) rotatably journalled in suitable bushing members. In the embodiment illustrated, the pumping gears 9 and 10 having integrally formed therewith hollow journal shafts ill. and 12, respectively, and the right portions of the journal shafts 11 and 12 are received in conventional, flanged bushings l3 and 14 mounted in the right portions of the gear chambers 7 and 8. The left portions of the gear journals 11 and 12 are received, respectively, in axially adjustable, pressure loadable bushing assemblies 15 and 16 mounted in the left sides of the pumping gear chambers '7 and 8. Bushing assemblies 15 and 16 are constructed in accordance with the present invention and will be described in detail hereinafter. In the embodiment illustrated, the lower pumping gear 10 is the driving gear and, accordingly, the left end of gear journal 12 has formed thereon a splined coupling termination 17 whereby the shaft may be drivingly connected to a suitable power source. Low pressure liquid is introduced into the pump housing at inlet 18 and high pressure liquid is discharged through outlet 19, the inlet and outlet passages communicating, respectively, with the inlet and discharge of the inte meshing pumping gears.

As the bushing assemblies 15 and 16 are essentially identical, only the bushing assembly 15 will be described in detail. The bushing assembly 15 comprises a barrel or body portion 22 and a cover member 23 mounted in overlapping relation on the right end of the barrel portion, as viewed in Fig. 1. Cover member 23 is of generally cylindrical or disc-like configuration and has formed therethrough an axially extending aperture 24 of suflicient diameter to receive gear journal shaft 11. In practice, the diameter of the aperture 24 is made slightly greater than the peripheral diameter of the shaft 11 to permit slight angular adjustment of the cover member with respect to the axis of the shaft to accommodate for misalignment as explained in detail in Lauck et 211., my application S. N. 28,646, filed May 22, 1948, now Patent No. 2,527,941. A short, downwardly extending groove 23a is formed in the lower side of the gear side face engaging surface of cover 23 and is located slightly to the left, as viewed in Fig. 2 of the transition point of the gear teeth whereby this groove and aperture 24 are in communication with inlet pressure.

As may be best seen in Figs. 2 and 3, the cover member 23 has formed in the left side thereof, as viewed in Fig. l, a deep, cylindrical recess 2%, the axis of which is offset with respect to the axis of aperture 2 As Will be apparent hereinafter, the extent to which the recess 25 is ofiset depends on the gradient to be compensated. The recess 25 is offset to the left, as viewed in Fig. 2, thus reducing the width of the pressure loadable motive surface designated 26 on the side thereof adjacent the inlet 18 of the pump, but correspondingly increasing the width of the motive surface 2:: on the side thereof adjacent the discharge outlet 19 of the pump. Cover 23 fits closely the inner diameter of chamber 7 formed in the pump housing, suflicient clearance, however, being provided to permit axial movement of the cover member with respect to the housing to permit the forward surface of the cover to engage the pumping gear side surfaces in sealing relation.

The barrel portion 22 of the bushing assembly is provided with an axially extending aperture 27 communicating at its right end with the aperture 24 formed in cover 23; however, the inner diameter of aperture 27 may be made somewhat less than the inner diameter of aperture 24 since it is desirable that the shaft 11 be journalled therein with a close, running fit. The axial groove 28 extending from the right to left ends of axial aperture 27 ensures suitable lubrication of the gear shaft 11. Near its left end, as viewed in Fig. 1, the barrel member 22 is provided with a deep, annular groove 30 which extends about its periphery and provides at its left side a flange 31 and at its right side a flange 32. The groove 3b is made as deep as possible without unduly weakening the bushing structure to reduce the weight of the assembly and at the same time to expose a greater surface area of the assembly to the fluid being pumped, thereby aiding in maintaining the bushing at a low temperature.

The flange 32 extends radially outwardly substantially further than the flange 31 and its extended portion seats at its left side, as viewed in Fig. l, on an annular shoulder 3. of the pump housing bore. The body or barrel portion of the assembly is thus securely supported in the pump housing bushin. receiving cavity 7 and is relatively immovable with respect thereto in the normal operation of the pump. The right end surface of the large flange 32, as viewed in Fig. 1, has formed thereon a raised or protuberant portion or boss 34 which is received in the offset recess 25 formed in the cover member 23, the boss 34 being offset in similar manner. The boss 34 is complementary to and fits closely into the recess 25 in telescopic relation. Escape of pressure fluid from the surface 26 through such space as may be allowed between the sides of the boss 34 and the adjacent sides of the recess 25 to permit movement of the cover 23 is prevented by an O-ring seal 35 disposed in an annular recess 36 formed about the periphery of the boss 34. The O-ring seal permits relative movement of the cover 23 with respect to the barrel and particularly the boss thereof While maintaining a fluid tight seal. The boss could, of course, be provided on the cover 23 and the recess in the end of the barrel 22, where desired, and similarly the seal ring 35 could be carried in an internal groove formed in the recess as well as by the boss 34.

In order to provide initial loading pressure, a plurality of loading springs 37 are disposed in suitable recesses formed in the boss 34 and the cover element 23 to initially urge the cover element toward the adjacent side surface of the pumping gear 9. This provides the initial sealing engagement required. Immediately, however, upon pumping commencing, discharge pressure is communicated to the motive surface 26 of the bushing assembly through an axially extending passage 38 formed between the bushing assemblies 15 and 16 at the point of convergence of the peripheries of the large flanges of the two bushing assemblies on their right side, as viewed in Fig. 2, that is, the side adjacent the discharge passage 19 H and the adjacent housing wall. This discharge pressure being communicated to the motive surface 26 pressure loads the cover element and urges the cover element 23 to the right, as viewed in Fig. 1, to establish and maintain sealing engagement thereof with the gear side face in accordance with usual pressure loaded pump practice.

it will be understood that either sufficient clearance must be provided between the periphery of flange 31 and the adjacent walls of the pump housing or a suitable passage otherwise formed across the periphery of the flange to vent the chamber defined primarily by groove 39 to low pressure. In the absence of such venting, pressure would accumulate against the left surface of flange 32 as viewed in Fig. l, causing movement of the body portion 22 of the bushing assembly. Since it is desirable that the flange 31 cooperate with the flange 32 to establish and maintain alignment of the bushing in the bore, preferably an axially extending groove Jill-a is formed in the periphery of each flange 31, the left end of each groove 31-a being then in communication with a low or intermediate pressure zone or" the pump through the axially extending passage se ts.

in the associated gear journal, as described in detail in the aforementioned patent to Roth et al.

Since, as stated hereinbefore, the force exerted by the pressure acting on the pressure loadable motive surface 26 is determined by the pressure and the extent of the area against which it acts, and because the portion of this area adjacent the inlet side of the pump, is quite narrow in extent as is readily evident from Fig. 2, as compared to the portion of the motive area adjacent the outlet side of the pump, it will be evident that the force acting in the direction of establishing a seal will be less on the pump inlet side of the bushing cover member, than on the pump discharge side thereof. The value of this pressure loading force will increase from a minimum value adjacent the pump inlet side of motive surface 26 to a maximum value adjacent the pump discharge side of the motive surface. The pressure loading force gradient can be made by controlling the relative areas of the portion adjacent the inlet and of the portions adjacent the outlet across the motive surface to correspond substantially in gradient to the pressure forces effective across the forward or gear side face engaging surfaces of the cover. At the same time, the total extent of the area 26 is selected so that the pressure loading force exceeds the oppositely directed force on the gear side face engaging surface of the cover element to provide the net sealing force required to establish an adequate pumping seal in accordance with usual pressure loaded pump practice.

it has been found in practice that it is sometimes necessary, in order to establish the optimum balance, to pro vide a beveled area 39 extending partially around the periphery of the forward surface of the cover element on the side thereof adjacent the outlet 19. The beveled area extends in a counter-clockwise direction from the discharge side of the pump toward the inlet side, as viewed in Pig. 2, and the location of the left terminus of the beveled area is selected to place this end of the beveled area in communication with a zone of relatively low pressure. In addition, the forward or gear side face engaging surface of the cover 23 may be grooved or relieved and the grooved or relieved areas vented to inlet pressure to reduce the effective pressure area on this surface, as set forth in the hereinbefore referred to Roth et al. patent.

It will be evident that since the eccentric area at the base of recess 25 is vented to inlet pressure through aperture 2 and groove 23a any pressure fluid from the discharge side of the pump leaking past the seal 35 will be vented to inlet pressure. At the same time, inlet pressure will be effective on this recessed area to urge this side of the bushing cover against the adjacent gear side face with a force proportional to the inlet pressure.

In order to facilitate description, the bushing assembly 15 has been described as generally cylindrical in configuration, this being the conventional pump bushing configuration. it will be understood however, that the present invention is equally adaptable to either curvilinear or angular construction and similarly the recess 25 and boss 3 may have a curvilinear or angular configuration. Generally, however, the cylindrical configuration shown is more readily adaptable to mass production techniques.

From the foregoing, it will be evident that the bushing assembly of this invention may be constructed so as to require no modification of the conventional pressure loaded type pump housing bushing receiving cavity and, accordingiy, the bushing is interchangeable with the usual type of bushing. it will be apparent, also, that by virtue of this interchangeability feature, it is feasible to provide several sets of bushing assemblies having different dispositions or proportionings of the motive surfaces so that by using one or the other of said sets, the pump may be adapted to accommodate for a wide range of force gradients across the forward surfaces of the bushings.

While this invention has been described particularly in conjunction with a pressure loadable intermeshing gear type pump, it will be evident that it is equally applicable to vane type pumps employing a pressure loadable end plate.

Where herein the various parts of this invention have been referred to as being located in a right or a left position, it will be understood that this is done solely for the purpose of facilitating description and that such references relate only to the relative positions of the parts as shown in the accompanying drawings.

While but one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed is:

l. A fluid pump comprising a housing, an inlet leading to and an outlet leading from said housing, means including a rotatable member received in said housing efliective to force fluid from said inlet out of said housing through said outlet, end plate means received in said housing and adapted to engage the side surface of said rotatable member in pumping seal relation comprising a rst member and a second member assembled in telescopic relation, one of said first and second members being axially movable with respect to said rotatable member and the other of said first and second members, means defining a pressure motive chamber between said first and second members eccentric to the axis of rotation of said rotatable member, and means continuously effective to direct pressure liquid generated by said rotatable member to said pressure motive chamber for urging said one of said first and second members in the direction of the adjacent gear side face.

2. A fluid pump comprising a housing having a pump chamber formed therein, said housing having an inlet leading to and an outlet leading from said pump chamber, means including a rotatable member received in said pump chamber effective to force fiuid from said inlet out of said housing through said outlet, an end plate assembly received in said pump chamber and adapted to engage the side surface of said rotatable member in pumping seal relation comprising a cover member and a barrel member assembled in telescopic relation, said cover member being axially movable with respect to said rotatable member and said barrel member, a first surface area on said cover member facing away from said rotatable member and normally spaced from the adjacent end wall of said barrel member, a second surface area on said cover member engageable with the adjacent side face of said rotatable member to provide a pumping seal therewith, said second surface area being subject to a pressure gradient extending from a minimum value adjacent the inlet of the pump chamber to a maximum value adjacent the outlet of the pump chamber, passage defining means continuously efiiective to direct pressure liquid generated by said rotatable member to the first surface area of said end plate assembly for urging the cover member of the end plate in the direction of the adjacent gear side face, and means including the center of said first surface area being offset with respect to the axis of rotation of said pumping element whereby the sealing force produced in response to application of pressure thereto is made to have a force gradient corresponding substantially and oppositely directed to the pressure gradient across the second surface area.

3. A fluid pump comprising a housing having a pump chamber formed therein, said housing having an inlet leading to and an outlet leading from said pump chamber, means including a rotatable member received in said pump chamber and efiective to force fluid from said inlet out of said housing through said outlet, an end plate assembly received in said pump chamber and adapted to engage the side surface of said rotatable member in pumping seal relation comprising a cover section and a barrel section assembled in telescopic relation, said cover section being axially movable with respect to said rotatable member and said barrel section, a boss on the side of said barrel section, a recess in said cover section complementary to said boss, said boss being received in said complementarily formed recess in said cover section, the center of said recess being offset with respect to the axis of rotation of said rotatable member, and the periphery "of said recess substantially encircling said axis, a first pressure responsive surface area provided by the surface of said cover section adjacent the end of said barrel section and surrounding the boss, at second surface area on said cover section engageable with the adjacent side surface of said rotatable member to provide a pumping seal therewith, said second surface area being subject to a pressure gradient extending from a minimum value adjacent the inlet of the pump chamber to a maximum value adjacent the outlet of the pump chamber, and passage defining means continuously effective to direct pressure liquid generated by said rotatable member to the first surface area of said end plate assembly for urging the cover section of the end plate assembly in the direction of the adjacent rotatable member side face.

4. A fluid pump in accordance with claim 3 wherein sealing and packing means are associated with said recess and said boss to prevent leakage of fiuid therebetween.

5. A fluid pump in accordance with claim 3 wherein the rotatable member side surface engaging surface of the cover section is beveled along the edge thereof adjacent the outlet side of the pump to define an area subject to the pressure generated by said rotatable pumping element to control the effective pressure area of the second surface area. I

6. A fluid pump comprising a housing for enclosing a rotatable pumping member, said housing having a pump chamber formed therein symmetrically disposed with respect to said rotatable member, said housing having an inlet leading to and an outlet leading from said pump chamber, an axially apertured pressure loadable bushing assembly receivable in said pump chamber and adapted to engage at its forward surface the adjacent side surface of said rotatable member in sealing relation, said assembly comprising a cover member and a barrel member, said cover member being axially movable with respect to said rotatable member and said barrel member, said cover member having a recess formed on the rear side thereof, a complementary boss on said barrel member disposed in said recess, an annular pressure responsive motive surface substantially encircling said axial aperture and extending radially of said recess and said boss and having the area thereof adjacent the inlet side of said pump reduced as compared with the area thereof adjacent the outlet side of said pump, and conduit defining means continuously effective to direct discharge pressure generated by said pump to said motive surface area.

7. A fluid pump of the type including a housing having an inlet and an outlet port formed therein, a rotatable pumping member journalled in said housing for transferring fluid from said inlet to said outlet port, end plate cfiniug means adapted to engage said pumping member in sealing relation, said end plate defining means including a cover member and a barrel member assembled in telescopic relation, said cover member being axially movable with respect to said rotatable member and said barrel member, said cover member being adapted to' engage at its forward surface said rotatable pumping member in sealing relation, a substantially continuous, generally annular motive surface formed on the rear surface or" said cover member, a substantially continuous generally annular, forward surface on said barrel member, said motive surface and said barrel member forward surface defining together with said housing a motive chamber, said motive surface being adapted in response to application of pressure to said motive chamber to urge said cover member toward said rotatable pumping member to establish said sealing relation, and conduit defining means for continuously communicating pressure generated by said pump to said motive chamber, said motive surface having a generally circular periphery concentrically disposed with respect to the axis of rotation of the pumping member and a generally circular, inner periphery eccentric'ally disposed with respect to the axis of said pumping member, said inner periphery having its center offset toward said inlet port.

8. A pressure loadable bushing assembly comprising a cover member and a barrel member, said assembly having an aperture extending axially therethrough, the outer periphery of said barrel member and said cover member being equal and defining a cylinder, said cover member having a recess formed on one side thereof, a complementary protruding portion of said barrel member adapted to be received in said recess, said recess and said protruding portion having their centers offset with respect to the axis of said axially extending aperture, the inner peripheries of said recess and said protruding portion substantially encircling said axis.

9. A pressure loadable bushing assembly comprising a cover member and barrel member, said assembly having an aperture extending axially therethrough, said cover member having a recess formed on one side thereof, a complementary protruding portion of said barrel member disposed in said recess, said recess and said protruding portion having their centers offset transversely with respect to the axis of said axially extending aperture, the peripheries of said recess and protruding portion substantially encircling said axis, and means disposed between said cover member and said barrel member for urging said cover member and said band member apart, said barrel member and said cover member having equal outer peripheiies and together defining a bushing assembly of cylindrical contour.

10. A pressure loadable bushing assembly for a rotatable pumping element comprising a cover member and a barrel member assembled in telescopic relation, the outer peripheries of said cover member and said barrel member defining a cylinder, said assembly being adapted to engage a pumping element in sealing relation at the cover member end thereof, and a generally annular surface area at the opposite end of said cover member adapted to be subject to pressure generated by said pumping element, said last mentioned surface area having its center offset with respect to the axis of said assembly and its periphery substantially encircling said axis.

11. A pressure loadable bushing assembly comprising a cover member and a barrel member, one of said members having a recess formed in the end surface thereof disposed intermediate the ends of said assembly and the other of said members having a complementary protruding portion adapted to be received in said recess whereby said members are assembled in telescopic relation, the outer periphery of said assembled members defining a substantially cylindrical assembly, said recess and said protruding portion being disposed radially inwardly of the periphery of said assembly and having their centers offset with respect to the center of said assembly, and a surface area on said cover member on the end thereof intermediate the ends of said assembly adapted to be subject to liquid pressure, said last mentioned surface area having its outer periphery defined by the periphery of said cover and its inner periphery defined by the periphery of said protruding portion.

12. A high pressure pump including a body and a cover providing a pumping cavity with an inlet and an outlet, bearing means for said pump cavity each defining an end plate portion and a tubular bearing portion a portion of which is eccentrically off-set relative to said end plate portion toward the inlet of the pump to provide a face outwardly of the pumping cavity on the end plate portion which increases in width toward the pump outlet, said bearing means and said body together forming a chamber behind said-end plate portions, means providing a passage in communication with the pump discharge and said chamber, whereby pressure forces in the pumping cavity tending to shift the end plate portions away from the pumping cavity will be balanced by pressure forces in said chamber which increase from the inlet to the outlet sides of the pump, a first sealing means between said cover and said body to prevent leakage therebetween, and a second sealing means surrounding said tubular bearing portion to prevent leakage from said chamber.

13. A high pressure pump including a body providing a pumping cavity with an inlet and an outlet, hearing means for said pump cavity each defining an end plate portion and a tubular bearing portion a portion of which is eccentrically off-set relative to said end plate portion toward the inlet of the pump to provide a face outwardly of the pumping cavity on the end plate portion which increases in width toward the pump outlet, said bearing means and said body together forming a chamber behind said end plate portions, means providing a passage in communication with the pump discharge and said chamber, whereby pressure forces in the pumping cavity tending to shift the end plate portions away from the pumping cavity will be balanced by pressure forces in said chamber which increase from the inlet to the outlet sides of the pump, a first sealing means surrounding said bearing means and a second sealing means surrounding said tubular bearing portion and coacting with said first sealing means to prevent leakage from said chamber.

14. A high pressure pump including a body providing a pumping cavity with an inlet and an outlet, bearing means for said pump cavity each defining an end plate portion and a tubular bearing portion a portion of which is eccentrically off-set relative to said end plate portion toward the inlet of the pump to provide a face outwardly of the pumping cavity on the end plate portion which increases in width toward the pump outlet, said bearing means and said body together forming a chamber behind said end plate portions, means providing a passage in communication with the pump discharge and said chamber, whereby pressure forces in the pumping cavity tending to shift the end plate portions away from the pumping cavity will be balanced by pressure forces in said chamber which increase from the inlet to the outlet sides of the pump, a first sealing means between said bearing means and said body and a second sealing means surrounding said tubular bearing portion to prevent leakage from said chamber.

15. A high pressure pump including a body and a cover providing a pumping cavity with an inlet and an outlet, bearing means for said pump cavity each defining an end plate portion and a tubular bearing portion a portion of which is eccentrically off-set relative to said end plate portion toward the inlet of the pump to provide a face outwardly of the pumping cavity on the end plate portion which increases in width toward the pump outlet, said bearing means and said body together forming a chamber behind said end plate portions, means providing a passage in communication with the pump discharge and said chamber, whereby pressure forces in the pumping cavity tending to shift the end plate portions away from the pumping cavity will be balanced by pressure forces in said chamber which increase from the inlet to the outlet sides of the pump, and sealing means between said cover and said body to prevent leakage therebetween.

16. A high pressure pump including a body providing a pumping cavity with an inlet and an outlet, bearing means for said pump cavity each defining an end plate portion and a tubular bearing portion a portion of which is eccentrically off-set relative to said end plate portion toward the inlet of the pump to provide a face outwardly of the pumping cavity on the end plate portion which increases in width toward the pump outlet, said bearing means and said body together forming a chamber behind said end plate portions, means providing a passage in communication with the pump discharge and said chamber, whereby pressure forces in the pumping cavity tending to shift the end plate portions away from the pumping cavity will be balanced by pressure forces in said chamber which increase from the inlet to the outlet sides of the pump, and sealing means operatively disposed between said bearing means and said body to prevent. leakage therebetween.

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